1. Field of the Invention
The present invention relates to the stator windings of large dynamoelectric machines such as hydro-generators, and more particularly, to the insulation of the series connected stator coil end turns of such machines.
2. Description of the Prior Art
The rating of hydro-generators has been increasing rapidly over the last few years. Single-turn coils with Roebel transposition of the conductor strands are most suited for these larger ratings. The series connected end turns of this type coil are necessarily large and carry full coil current. These connections may be made by brazing individual strands or groups of strands from adjacent coils together in a compact manner. A more convenient method is to braze one or two copper bars between adjacent coils.
Such connections in the past have been insulated by means of hand taping with an insulating tape. However, because the insulation procedure must often be accomplished in the power plant, and because of the limited access to the terminal portions of the series connected coil end turns, the conventional hand taping process is unsuitable. Furthermore, because the joints conduct full coil current an insulating structure providing improved heat transfer is desirable. Of course, a suitable insulation scheme for the brazed structure should be impervious to moisture and oil and should occupy a minimum of space in order to avoid interfering with ventilation, and should be suitable for application under field conditions with semi-skilled labor.
As an aid to further understanding of the general construction and use of epoxy encapsulated conductors in dynamoelectric machines, reference is made to the following examples of the prior art:
(1) U.S. Pat. No. 3,151,260, D. C. MacCracken, Jr. et al;
(2) U.S. Pat. No. 3,555,316, Donald D. Bleich;
(3) U.S. Pat. No. 3,123,729, R. Fagel; and
(4) U.S. Pat. No. 2,944,297, J. T. Maynard.